Can anyone help me with the correct formula?

I6 = Time
E16 = Mean
E 1 = Std Dev

If E6 less than 1 and 1/2 std dev below mean, E6 = 10
If E6 less than 1 std dev below mean, E6= 7.5
If E6 greater than 1 std dev below mean, but less than mean, E6= 5
If E6 greater than men, but less than 1 std dev above men, E6 = 2.5
If E6 greater that 1 std dev above mean, E6 = 0

Simply put... lower time = higher score